Author Topic: gps data  (Read 428 times)

Offline Bob M

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gps data
« on: January 23, 2021, 08:43:07 AM »
When you add gps data to a raw file, it is stored in the xmp file.  When you add gps data to a jpeg, is it stored as xmp data, exif data, or both?

Offline dennis

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Re: gps data
« Reply #1 on: January 26, 2021, 09:29:00 AM »
It depends on the JPEG and whether it has an existing GPS table or not.  Many cameras that don't have GPS at least write a GPS table that is mostly empty.  If PM determines it can "easily" fill out this GPS table in Exif then it will add it there, otherwise it puts the GPS info in the XMP (which can always be done).  Modifying Exif tables is tricky since they are TIFF-based structures and by that design are not straightforward to modify.

HTH

Offline Bob M

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Re: gps data
« Reply #2 on: January 26, 2021, 01:24:39 PM »
Thanks Dennis

I asked more out of curiosity than need.  I'm trying to get my head around around why flickr stumbles over jpegs geotagged by PM.  My longtitude is about 77.5W; flickr puts me at 77.5E.  I suspect, but don't know for sure that flickr wants -77.5 rather than 77.5W.  So I have been trying to see if I can coerce PM to show that minus sign.  But without success.  (I tried to enter my longitude as -77.5E into PM.  PM displayed this correctly but stored it as 77.5W.). You guys have your standards and you stick to them  :).

Perhaps I could do something with exiftool, but that's more hoops than I want to jump through.  Including gps data with uploaded photos is not that big a deal and is, perhaps arguably, inappropriate.

Thanks again

Offline dennis

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Re: gps data
« Reply #3 on: January 26, 2021, 03:36:59 PM »
Hmm.

In Exif there are separate tags for whether North or South (for Latitude) or East or West (for Longitude).  Same with altitude (yes it can be negative).  The degree values are always a positive (absolute value) number, actually 3 rationals (x/y) for degrees, minutes and seconds. Very wonky.  GPS in XMP is more plain and simple text.

I guess I'd need to see a photo that is showing wrong in Flickr to diagnose.

Offline Bob M

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Re: gps data
« Reply #4 on: January 27, 2021, 07:41:05 AM »

In Exif there are separate tags for whether North or South (for Latitude) or East or West (for Longitude).  Same with altitude (yes it can be negative).  The degree values are always a positive (absolute value) number, actually 3 rationals (x/y) for degrees, minutes and seconds. Very wonky.  GPS in XMP is more plain and simple text.


That's basically where my original question came from;  I didn't think there was much opportunity for ambiguity in the exif data but perhaps there was in the xmp data.

For completeness, I am running PM+ V6 build 5446 on Windows 10.

I have attached a representative jpeg, the xmp file for its associated raw (orf) file, a screenshot showing where PM thinks the photo was taken and a screenshot showing where flickr thinks it was taken.

The jpeg was produced as follows:  I used RawThereapee to develop the raw file (an orf) into a jpeg.  The xmp data was added to the jpeg by PM (a combination of tools/update iptc/xmp ... (from raw) followed by some specific edits).  The gps data was added via a gpx file and file/import gps coordinates.

PM shows the location correctly.  Flickr has me in in Kazakhstan.